The present invention relates broadly to a digital waveform generator, and in particular to a non-linear digital waveform generator apparatus compensating for the Doppler dispersion due to a target's velocity.
In the prior art, the Doppler effect wherein a change occurs in the frequence of a detected sound, light or other electromagnetic wave which is caused by the relative motion between the source and the receiver, is well known. The Doppler effect has been utilized in many ways including airborne systems which are used to determine the velocity of the vehicle relative to the ground for such purposes as aerial mapping, bombing and navigation. Many ground-based radars utilize the effect to measure the relative velocity of a moving radar target with respect to the radar system. These radar units are operated upon the principle that the Doppler frequency shift in a target return is proportional to the radial component of the target velocity. However, target returns from a moving object are often masked or obscured by the effects of Doppler dispersion. Transmitted signals such as pulsed frequency modulated radar signals are comprised of varying frequencies which frequencies experience the greatest Doppler shift. The present invention provides a waveform generator apparatus to correct the effects of Doppler dispersion in target returns from a moving target.